Optimal preventive maintenance for wind turbines considering the effects of wind speed

This paper presents a preventive maintenance policy for wind turbines considering three effects of wind speed: accelerating hazard rate, restricting maintenance implementation, and affecting downtime cost. The effect on the hazard rate is described by a proportional hazards model. The restriction on maintenance actions results in the elongation of maintenance duration. The downtime cost is evaluated based on the power output curve model. Three failure types (i.e., catastrophic failure, critical failure, and minor failure) and multiple maintenance actions (i.e., preventive and corrective replacements, preventive and corrective general repairs, and minimal repair) are integrated into the policy. The objective is to determine the optimal maintenance policy that minimizes the long-run average cost rate. The optimization problem is formulated and solved in the semi-Markov decision process (SMDP) framework. A practical example is provided to illustrate the proposed method. The comparison with other policies shows the superiority of the proposed policy as well as the significance of the three effects of wind speed in maintenance decision-making.